Pbocess of making sulphuric acid



eb 7 w. F. LAMoRl-:Aux

PROCESS OF MAKING SULPHURIC ACID Original Filed March 9, 1925 dgiow NQJJ h1 H MJL C T mi jf E f MM H v DNN/l o n u F u J El .mu All I kN h 1m B w .l m m 5M we :SQ mdoiz 19;@ Tl 1 1L Kl ,i

smelting, roasting,

Patented Feb. 8, 1927.

UNITED STATES WILLIAM F.`LAMOREAUX, F ISABELLA, TENNESSEE.

PROCESS 0F MAKING SULPHURIC ACID.

Continuation of application Serial No. 14,305, led March 9, 1925.

This application filed .Tune 13, 1925.

Serial No. 36,907.

This invention relates to an improved process or method of producingsulphuric acid from sulphur dioxide obtained from the burning ofelemental sulphur, or from oxides of sulphur such as are contained invariable admixture with air in the gases generated by or liberated `fromany furnace, or calcining pyrite ores or other sulphur bearingmaterials.

In the manufacture of sulphuric acid by the well known chamber process,the sulphur dioxide is oxidized through the intermediary use ofOxy-nitrogen compounds which are used either in gaseous state or in theliquid state, i. e., in solution with sulphuric acid. These Oxy-nitrogencompounds act as pseudo-catalysts and accelerate the union of thesulphur dioxide with oxygen; but in the process these Oxy-nitrogencompounds are themselves reduced or decomposed and are thus liberatedinto the gaseous phase as lower oxides of nitrogen but principally asnitric oxide. In the gaseous phase, these lower oxides of nitrogen willescape to the atmosphere unless they be re-oxidized and absorbed, andthus recovered, in the Gay- Lussac tower which is ordinarily employedfor that purpose. y

It is well known that, owing to various disturbances which commonlyoccur in the acid making process, the Gay-Lussac tower rarely functionsperfectly for the complete absorption of the Oxy-nitrogen compounds, andconsequently there is almost at all times some escape of these compoundsto the atmosphere, thus resulting not only in a costly loss but alsocreating a noxious and disagreeable nuisance to surrounding habitation.

Furthermore, the Oxy-nitrogen compounds, whether having been partiallyor wholly absorbed in the Gray-Lussac tower, must subsequently bereturned to the acid making system to resume their rle as oxygen-carrersor catalysts and for this purpose the Glover tower is employed, but hereagain the purpose is but rarely completely or perfectly accomplished,due to the fact that the higher grades of sulphuric acid, i. e.4 acid ofhigher than about 58 B. gravity, are` not readily denitrated exceptthrough prolonged contact with sulphur dioxide and the application ofhigh temperatures; consequently the sulphuric acid leaving the Glovertower usuaily contains appreciable amounts of oxynitrogen compoundsstill in solution and 1n corresponding measure there results a loss ofthese compounds in the acid that is withdrawn from the system forcommercial use. Thus again, not only does a costly loss occur, but whensuch sulphuric acid, `containing even small amounts of Oxy-nitrogencoinpounds in solution, is used for various commercial purposes (i. e.in acid phosphate manufacture, in the pickling of iron or steel, or inthe manufacture of glycerine) many serious objections or evendifficulties arise so that such acid is not desired by the industrialtrade.

If, on the other hand, however, a complete denitration of the sulphuricacid is undertaken in the Glover tower through more prolonged contactwith sulphur dioxide, particularly at comparatively loW temperatures,the sulphuric acid will then usually be found to contain appreciableamounts of sulphur dioxide in solution and such acid is alsoobjectionable for certain industrial uses.

The denitrated and more concentrated acid obtained from the Glover toweris used in the Gray-Lussac tower for absorption of the Oxy-nitrogencolnpounds that would otherwise escape from the chamber system, and ithas commonly been found that the presence of either Oxy-nitrogencompounds or sulphur dioxlde initially present in solution in thesulphuric acid even in slightly appreciable amounts greatly interfereswith the absorption properties of the acid; it is obvious that evensmall amounts of Oxy-nitrogen compounds in solution in the acid will tothat extent diminish its total absorption power,- or, if any sulphurdioxide is initially in solution, it will inhibit absorption through thefollowing reaction:

the nitric oxide, NO, being but slightly soluble in the sulphuric acid,remains in the the atmosphere.

In my present invention I avoid the difficulties which usually occur inthe operation ofthe ordinary chamber acid process and also prevent theescape of noxious gases to the atmosphere; at the same time, I producesulphuric acid which is free from either oxynitrogen compounds orsulphur dioxide `and therefore more suitable to the requirements of theindustrial trade.

In my U. S. Patent No. 1,456,064, issued gaseous phase unabsorbcd and soescapes to llO LI A;

`claimed in my Patent No. 1,456,064.

`gases from the reacting chamber into an absorption tower similarlymechanically operated, and delivering theacid from the absorption towerto the reacting chamber', the acid liquid trom the reacting chamber tothe Glover tower and the `sulphuric acid from the Glover tower to theabsorption tower and `:to storage, all `as described and illustrated inthe specification and drawings ot' said Letters Patent. According to theabove disclosures, a Glover tower may be employed for the usual purposeolif denitrab ing and concentrating the snlphuric vacid kwhich is thenused tor absorption ot the nitrogen `oxides that have been liberated inthe course of the preceding chemical reactions.

Now, my present invention isa modification of and :improvement in themanufacture ot' sulphuric acid as disclosed in my Patent No. 1,456,064.I dispense with the use of the Glover tower entirely, 'for I havediscovered that th-ctreactions can be soconducted and controlled in thecourse of the oxidation of the sulphur dioxide that the acid is`entirely denitrated before leaving the apparatus wherein the reactionstake place, following which the Vacid can be thoroughly washed with air(or an inert gas such as carhon dioxide) to remove any trace of sulphurdioxide that otherwise might be lett dissolved in the acid, and the acidso delivered to the absorption apparatus `will possess the Vgreatestpossible absorption power for the removal and retention ott theoxy-nitrogen conipounds that are there to be recovered.

According to my invention, I employ oxynitrogen compounds, either in theoaseous state or in solution in a liquid state, or both, as the oxygencarriers or pseudo-catalysts wherewith, in the presence ot atmosphericoxygen, sulphur dioxide is utilized to produce sulphuric acid. The useot' Oxy-nitro'- gen compounds for this purpose is, of course,

well known in the art, but I believe I am the first to have discoveredor recognized and disclosed the enormously accelerated rate at whichsulphuric dioxide can be, oxidized and vconverted into sulphuric acid byintermingling the gas phase and liquid Vphase ,components of thesereactions in a statelt intensely high dispersion, as described yand Iachieve an intense dispersion of the'A two c phases such as maybeobtained, for'exainple,

. theemployment `of a `-high speed gas washer, e. g., a washer of theFeld type having a peripheral speed of 2,000 feet per minute. Vith suchan apparatus the liquid isdispersedxin the gas and the gas is alsodispersed in the liquid; the films so obtained are rapidly coalesced andtherefore a fresh surface is continuously exposed many times per second."Io shortly describe the condition thus produced I have used in theclaims the term intense highly dispersed phase contact.

An apparatus suitable for carrying out the process is shown in thedrawing, in which A designates the flue leading from the source oitsulphur dioxide (i. e., from a roasting furnace, sulphur burner, etc.),thence the sulphur dioxide bearing gases are led through the coolingpipe B where the teniperature of the gases .is reduced to approximatelythat ot the atmosphere, the exterior ot the cooling pipe B being cooledthrough exposure to the air or by means ot water. Any other method ofcooling the gases may, .ol course, be employed. rlhe sulphur dioxidebearing gases, after having been thus cooled, are then conducted throughthe flue i C, D, and D to the valves E and E which control the admissionand flow of the gases into the `Feld washers F and K. The Feld washer Fis divided .into two parts, S and S, separated in suchmanner that theliquid flowing through the upper parl' S can pass downward through pipe2O into and through Vthe lowerpart S', but `the gases entering S and Scannot inteimix,tlie object of this arrangement will be fully understoodin later discourse. That portion or' the gases which is admitted throughthe valve E passes intoand through S and thence by `means of pipe 'Ilinto the lower section. ol.: the Feld washer If. The valve E admits aportion of the sulphur dioxide bearing gases into the lowerl sectionoil' the zpparatus l also of vthe Feld washer type` where it unites withthe gases that enter through pipe Il. The, united flow oiE then pas.upward vthrough K, thence. through pipe Il into and through the Feldwasher M. thereupon .to enter the centrifugal ltan lT and 'to bedischarged to' theatmosphere through the exit pipe V(n). The apparatusIi and the upper V"part S otl apparatus F are employed 'for the purposeoi" oxidizing the sulphur dioxide Aand constitute the essential reactionappaand other gaseous city-nitrogen compounds are formed, and tol.recover these valuable ,compoui'ids the gases are conducted to theapparatush/ii'wherein are performed the rv yactions sought tolao-accomplished usually by l the use' otl Gay-Lussac towers. i. e., theoxi ,(lation, absorption and retention in solution Aof all ot' thegaseous oxy-nitrogen cornlpounds that' otherwiseY would escape toI theSti atmosphere. By means of centrifugal pumps, o perated according tothe usual practice in acid manufacture, the sulphuric acid is circulatedthroughout the plant as follows 1- thus, (u) the tank 1l containsnitrous vitriol which has been pumped from tank 7 by means of pump 10,and from tank ll the acid is admitted into the top of the Feld washer Fwherein it flows downward from one section to another at the same timeencountering in counter-flow direction the ascending sulphur dioxidebearing gases that enter through the valve E. The flow ot' n1- trousvitriol entering F is so regulated both as to quantity and qualityA ofniter content that upon entering S it will have been en-` tirelydenitrated accordingto the reaction: QHSNO-pern(),LSOFeHgsOQNO 'lheliberated nitric oxide, NO, together with the residual gases, isconducted by pipe H to the, lower section of apparatus K where it uniteswith more sulphur 4dioxide admitted through valve E. The admission ofgas through valve E is so regulated that the nitrosity ot' the acidflowing into tank 7 (part of which is pumped to tank 11) may be kept ata predetermined amount and thereby governing also the quantitative X1-dation of the sulphur dioxide and its complete conversion into sulphuricacid, and which in turn depends upon the sulphur dioxide content ot' thegases being treated. The denitrated acid entering and flowing downwardthrough S encounters in counteriiow direction an ascending liow of airinduced through pipe l)` by means ot the centrifugal fan R; a sufficientvolume ot' air being thus passed through S to thoroughly and completelydisplace and remove any trace of city-nitrogen compounds or sulphurdioxide that might otherwise be retained in solution in the acid, anddischarged through pipe T; by this means the acid flowing to tank l isentirely tree ot-either of these compounds so that upon being deliveredby means ot' pump 2 to tank .3 it is in the most desirable condition forfurther use in `the recovery of Oxy-nitrogen compounds in apparatus M,or tobe transferred to the storage tank l2 for commercial use; and (o)the sulphur dioxide bearing gases ascending through apparatus Kencounter the descending flow ot' strong nitrous vitriol that isadmitted from tank (i, the latter flow of nitrous vitriol is alsoaugmented by the superimposed low of weaker nitrous vitriol which iscontinuously pumped `trom tank 7 by means ot' pump S to tank 9 andthence {lowing into one of the mid-sections of apparatus K, It will beobserved that the gases rich in sulphur dioxide and oxygen enteringapparatus F and also apparatus K are brought into contact with theweaker nitrous vitriol, while they ascend through the apparatus, theycome into contact with nitrous vitriol of gra-dually increasingstrength; by this means the chemical equilibrium ot' this reaction canbe progressively governed and maintained throughout, 'resulting finallyin the complete or substantially complete oxidation of the sulphurdoxide; and (c) the gases leaving apparatus K will contain in admixturevarious gaseous Oxy-nitrogen compounds which should be recovered,-theyare therefor-e conducted through pipe L to the apparatus M where theyare caused to asc-end in counter-current direction in contact with thedescending flow of sulphuric acid admitted from tank 3. The strongnitrous vitriol thus formed flows -to tank t and from there is elevatedto tank by means of pump and (el) through the pipe V there may beintroduced into the system additional amounts of Oxy-nitrogen compoundssuch as may be required from time to time to make up any depletion thatnormally occurs through the gradual loss of these compounds, the amountadded being so regula-ted that the total amount of Oxy-nitrogencompounds in circulation in the plant is at all tim-es kept definitelyproportioned to the amount of sulphur dioxide to `be oxidized; and (e)water is, of course, introduced into the system as and when required tomaintain the proper working conditions and to supply the chemicalreaction requirementsthe introduction ot the water being usually madeinto the top section ot' apparatus F as indicated; and (f) for thepurpose of cooling the acid, cooling or refrigerating coils may beplaced in any or all of the tanks l, 3, et, 6, 7, 9 and 1l andapparatuses E, K- and M shown in the accompanying drawing. By means ot'such an acid circulating system, the proper quantities and qualities ofcirculating acids, cooled to the proper working teniperatures, can beeasily kept under control so as to maintain a uniformity ofquantitativ-e and qualitative Yfactors'throughout the whole cycle of thechemical reaction; for, owing to the rapid circulation of both thegaseous and the liquid materials and the conveniently afforded means ofregulating the quantities of these materials in varying proportion toeach other, -faulty conditions of operation can bc promptly ascertainedand corrections as promptly made, this elasticity ol' control being'ofthe greatest importance in the manufacture of sulphuric acid.

The arrangement of the upper and lower portions, S and' S respectively,in the one piece of apparatus il" as shown is but illustrative of onemethod of arrangement for economical reasons in the case of a plant ofcomparatively small output, whereas in a plant of larger output two Feldwashers might he employed, each respectively to perform the functionsdescribed for S and S.

And although I have chosen the Feld Washer ot' vertical type ,toillustrate one method of carrying `my invention into eiiect, I mayemploy any one ot several Well known rotary or centrifugal types `ot gasWashersg indeed, any type ot apparatus that will produce such a state ofhigh dispersion as to present the extreme area of reacting surfacebetween the gases and liquids may be usedk to carry out the purpose ofmy-invention but it is quite essential that `With Whatever type otapparatus that may be used there shall be etlected a continuouslyproceeding method ot dispersing the liquid phase components in order toproduce newly formed surface films for the adsorption of the gaseousphase components and immediately or simultaneously causing the`disruption ot such adsorbed films substantially as soon as formed, bycoalescence `rin acollecting mass of liquid, said dispersion andco-alescence continning in `a rapidly repeated cyclic order.

Referring to the apparatus illustrated in the drawing accompanying thisspecification, within which the various reactions are caused to takeplace, it ivill be understood `that the sizeand shape oi' the apparatus,the construction and general. arrangement of the internal stationary ormovable parts, the location and size of the inlet and outlet openingstor the Vadmission and escape of the gases and liquids, and whether saidopenings are soarrangedas to cause the gases to .pass vertically upwardor downward or to pass Vhorizontally through or over the liquids, haveno specific bearingupon the principle of my invention other than to showone .Way Aby which it is carried into elicct, and

may be materiallymodilied Without in the least departing from the scopeof my invention.

This application is a continuation ot my application Serial No. 14,305,liled March 9,1925.

I claim:

l. In a process for making sulphuric acid, the method Which consists inthe following steps: (l) bringing sulphur dioxide containing gases intointimate highly dispersed phase Contact `With nitrous vitriol regulatedin quantity and quality so that the resulting sulphuric acid `iscompletely denitrated; (2) subjecting the thus produced acid to intimatehighly dispersed phase contact With a 'current of gas to remove anyresidual sulphur dioxide gas; and (3)' collecting the rcsultingpurified.sulphuric acid.

2. In a process for'malring sulphuric acid the method which consists in(l) bringing gases containing sulphur dioxide into intimate highlydispersed phase contact with nitrous vitriol regulated in quantity andquality so that the resultingsulphuric acid iscompletely denitrated; (2)producing :sa-id `nitrous avitriol by bringing nitrous gases reif/,alie

from `the denitrating operation and a regulated 4quantity of `gasescontaining sulphur dioxide in ascending tloiv into intimate highlydispersed phase contact with down-flowing nitrous vitriol of graduallyincreasing strength; (3) passing at least a part ot the thus producednitrous vitriol to the denitrating` operation; (4l) absorbing gaseousOxy-.nitrogen compounds resulting trom said second step by intimatehighly dispersed phase contact with sulphuric acid; and (5) delivering`the nitrous vitriol :from `the absorbing operation to the second step.

3. In a process for making sulphuric acid tlieistep ot' producingnitrous vitriol of predetermined quality which consists in bring`trating thereinaining portion to form sulphuric acid.

5. In a process for making sulphuric acid, the method of producingnitrous vitriol of predetermined strength which consists in bringinggases containing nitrogen oxides an-d regulated quantities ot gasescontaining sulphur dioxide into intimate highly dispersed phase contactin counter-current flow and in successive stages, introducing nitrousvitriol at an intermediate stage and stronger nitrous vitriol at a laterstage, collecting the nitrous vitriol at `the initial stage and removingthe nitrous gases at the final stage.

`6. In amethod as claimed in claim 5, the method which` comprises`al'isorbing the nitrous gases in sulphuric acid toproduce said strongernitrous vitriol.

7.v The process of purifyingsulphuric acid from sulphur dioxide whichconsists in passing -a current of gas therethrough to carry ott thesulphur dioxide.

8. The process as claimed in claim 7 in which the acid is subjected tointimate highly 4dispersed phase contact with the current of gas 9.Thefprocess of denitrating nitrous vitriol Which consists in contactingthe nitrous ifitriol-With:sulphur dioxide containing gases in such:proportions and under such conditions as `to produce completedenitration, and thereafter contacting the denitrated acid Withagas freefrom sulphurdioxide and oxides of nitrogen to remove sulphur dioxidefrom the acid.

l0. In processes of making sulpliuric acid involving the use of oXidesof nitrogen, the steps which consist in contacting at least a part ofthe sulphur dioxide containing gas supply with nitrous vitriol producedin the process in such proportions and under such conditions as toproduce complete denitration, contacting the denitrated acid With air toremove sulphur dioxide therefrom, and using at least a part of theresulting acid for absorbing oxides of nitrogen.

11. In a process for making sulphur-ic acid the steps Which consist incontacting a part of the sulphur dioxide containing gas supply withnitrous vitriol produced in the process in such proportions and undersuch conditions as to produce complete deuitration contacting theresulting denitrated acid with air to free it from sulphur dioxide,contacting the gases resulting from the denitrating step and theremainder of the sulphur dioxide containing gas supply with acountercurrent ioW of nitrous vitriol of progressively increasingstrength, contacting the resulting gases with at least a part of theacid produced by contacting the denitrated acid with air and deliveringthe resulting acid to said countercurrent flow of nitrous vitriol, anddelivering at least a part of said countei-current How of nitrousvitriol to the dcnitrating step.

In testimony whereof, I aix my signature.

IVM. F. LAMOREAUX.

